From Medieval Latin *ianuella*, a diminutive of *ianua* ("door, gate, entrance"), itself from *Ianus*, the Roman god of doorways and transitions. The shift from "door" to "window" reflects how both were seen as openings to the outside world.

In Brazil and Portugal alike, *janela* appears in countless everyday expressions. Notably, *assento de janela* (window seat) is a much-coveted spot on buses and planes. In computing, Portuguese adopted *janela* as the word for a software window — making it doubly useful for modern learners. Note: Spanish speakers should be careful — the Spanish false friend *ventana* (window) has no overlap with *janela*; the Portuguese word *janela* more closely echoes the Italian *finestra* in its Latin origin story.